Uh, I think you've got things mixed up. The PSP version has the 2D sprites, and the DS version is 3D.
I suspect it'll be the DS/3D version because they've ported that one before; it's already on Android and iOS, both of which are much easier to port to PC than a PSP game is. But the PSP/2D version looks better, has better music, has no voice acting instead of crap voice acting, and includes The After Years. It's superior in pretty much every regard.